The present invention relates to the field of system networks, and, more particularly, to a method and apparatus for allocating bandwidth to systems transmitting data over a communication link in a network.
In a network, such as the Internet or an Intranet, in which many systems are coupled to each other by communication links, some links may be overused, that is, the demand for bandwidth over a particular link exceeds the bandwidth that is actually available. Often, this demand results from several data flows, possibly originating from multiple sources competing for the available bandwidth. Accordingly, it is desirable to enforce a specific policy for allocating the available bandwidth among the competing sources.
Typically, the bandwidth allocation policy is performed either at the systems sending the data flows or at intermediate routers in the network. Examples of mechanisms for allocating bandwidth among data flows include xe2x80x9cfair queuingxe2x80x9d, xe2x80x9cweighted fair queuingxe2x80x9d, and xe2x80x9cvirtual clockxe2x80x9d. Some of these approaches aim at achieving simple fairness among flows, while others can favor one data flow over another.
Such approaches, however, are inadequate when the system receiving the data flows wants to prioritize those data flows. For one, the sending system may not be aware of the desired priorities of the receiving system, and thus send data contrary to those priorities. Further, if multiple sending systems are sharing the link, it can be quite difficult for the sending systems to coordinate their bandwidth allocation policies to match the bandwidth allocation desired by the receiving system, particularly if these sending systems do not have a mutually agreed upon framework for expressing priorities.
One example of such a situation would be a Web proxy server, between an organization and the Internet, which is connected to the Internet via an overutilized link. The proxy operator may wish to give higher priority to retrievals requested by specific users.
Another example is a Web browser with several active windows, one of which is conveying low-priority periodic status updates, and the other is used for explicit requests for information. If the browser is connected via a slow link (such as a modem), the user may want to give priority to responses to the explicit requests, instead of the status updates.
Thus, there remains a need for a method and an apparatus that enables a receiving system to achieve its own bandwidth allocation policy among multiple sending sources sharing a communication link.
An object of the present invention is to give the receiver of flows of data packets the capability to control the bandwidth allocation among multiple users of a network sharing a common communication link. Thus, the receiver can enforce its own bandwidth allocation policy without the need of flow-setup protocols or having to communicate the bandwidth policy to routers in the network. Further, the invention has the advantage of not necessarily requiring changes to existing sending systems or routers.
The present invention relates to methods and systems for allocating bandwidth on a communication link in a network operating according to a flow-controlled protocol where a receiving system receives a flow of data packets from a sending system via the communication link. The receiving system determines a target bandwidth to be allocated to the flow on the link and transmits data to the sending system. The transmitted data provides feedback to the sending system such that when the sending system transmits subsequent data packets to the receiving system in response to the transmitted data, data is transmitted by the sending system to the receiving system at a rate approximating the target bandwidth.
In one embodiment of the method, the data transmitted by the receiving system to the sending system acknowledges receipt of a particular data packet in the flow of data packets.
In another embodiment of the method, the data transmitted from the receiving system to the sending system indicate a maximum amount of data that the receiving system will accept from the sending system in a subsequent data transmission. The maximum amount is determined so that when the sending system transmits subsequent data packets according to that amount, data is transmitted by the sending system to the receiving system at a rate approximating the target bandwidth.
In still another embodiment of the method, a rate at which the transmitted data from the receiving system arrive at the sending system determines the rate at which the sending system transmits the subsequent data packets.
In still yet another embodiment, the method calculates a period of time for which the receiving system does not transmit data to the sending system. The delay is from when the receiving system would normally transmit the data operating according to the network protocol. The transmission of subsequent data packets on the link by the sending system is thereby delayed for the period of time, causing the data transmission rate of the sending system to approximate the target bandwidth on the link allocated to the flow. In one embodiment of the invention, the method assigns the flow to a class of flows, and the calculated period of time applies to each flow in that class.
The invention may be implemented in a system including a network interface for receiving a flow of data packets from a sending system on the network via the link. A processor, coupled to the network interface, determines a target bandwidth to be allocated to the flow on the link. The network interface transmits data to the sending system in response to receiving the flow of data packets. The data transmitted by the interface controls the sending system such that the sending system transmits subsequent data packets at a rate corresponding to the target bandwidth allocated to the flow.